The partition layout doesn't have to be *identical*, however the sizes of each slice need to be the exact same amount of blocks.
Also, do you *never* plan on mirroring the other partitions? (P.S: "Quote" tags suck for code, use [code] tags)
Most people would want to use the same slice-numbers just to avoid confusion (nothing like 'accidentally' resync'ing the wrong metadevices to earn a smoke break in the morning!)
prtvtoc /dev/rdsk/c0t0d0s2 | fmthard -s - /dev/rdsk/c0t2d0s2
By the way, you're going to need a tiny slice to store your metadb's. I'd suggest 32mb, and 3 metadb copies. You'll need that slice unmirrored, and on both disks.